In fault tree analysis, which logic functions are used to evaluate risks in a process?

In fault tree analysis, which logic functions are used to evaluate risks in a process?

• A. XOR and NAND
• B. OR and AND
• C. NOT and NOR
• D. OR and NOR

Answer: (B)

In fault tree analysis, risks are built from a boolean network of events using logic gates to show how faults combine to produce a top event. The most important gates are OR and AND. An OR gate means that if any one of the input failures occurs, the output event happens, capturing multiple independent ways a risk can arise. An AND gate means that all of the input failures must occur together for the output event to happen, representing scenarios where joint or interdependent faults drive the risk. Together, these gates let you model both alternative routes to failure and the need for multiple conditions to occur, which is essential for evaluating overall risk. Other gates like XOR, NOR, and NAND aren’t the standard building blocks for the basic fault-tree structure, and NOT is used for negation or modeling protective actions rather than as a primary way to combine multiple causes.

In fault tree analysis, risks are built from a boolean network of events using logic gates to show how faults combine to produce a top event. The most important gates are OR and AND. An OR gate means that if any one of the input failures occurs, the output event happens, capturing multiple independent ways a risk can arise. An AND gate means that all of the input failures must occur together for the output event to happen, representing scenarios where joint or interdependent faults drive the risk. Together, these gates let you model both alternative routes to failure and the need for multiple conditions to occur, which is essential for evaluating overall risk. Other gates like XOR, NOR, and NAND aren’t the standard building blocks for the basic fault-tree structure, and NOT is used for negation or modeling protective actions rather than as a primary way to combine multiple causes.